The present invention relates to a paper handling apparatus for use with a copier, printer or similar equipment for sorting a number of paper sheets sequentially driven out of the equipment to prepare paper stacks and binding the paper stacks.
Paper sheets driven out of a copier or a printer, for example, have customarily been stacked on individual bins of a sorter or stacker. The stacks of paper sheets are removed from the bins one by one and then bound together by a stapler, punched and then fastened, or bound together by paste. However, picking up the paper stacks one by one out of the bins for binding or otherwise treating them is troublesome and not efficient. A recent achievement in the realm of equipment of the kind described is a paper handling apparatus capable of stapling or otherwise handling paper stacks within bins thereof and, in this sense, sometimes referred to as a sorter and stapler. Typical of this type of paper handling apparatuses is an apparatus which distributes a predetermined number of paper sheets to each of all of the bins and then staple the paper sheets bin by bin, as disclosed in Japanese Patent Laid-Open Publication (Kokai) Nos. 62-290655, 63-60871, and 63-116168. A copier with such a sorter and stapler is generally provided with a function of positioning the paper sheets distributed to the bins. Should the paper sheets be not positioned or neatly arranged on the individual bins, the stapler would fail to bind them neatly. To promote efficient stapling, an arrangement may be made such that as soon as a paper sheet associated with the last document enters the first bin, a stapling operation begins at the first bin without awaiting the delivery of a predetermined number of paper sheets to all of the bins.
The copier with a sorter and stapler is often operable in two different stapling modes, i.e., an automatic staple mode and a manual staple mode. The automatic staple mode binds, in combination with an ADF (Automatic Document Feeder) mode, paper stacks automatically after the last copy has been copied. The manual staple mode is selected in combination with a cover plate mode or an SADF (Semi-Automatic Document Feeder) mode and is contemplated such that after the last document has been copied in a sort mode, a stapling operation begins in response to the manipulation of a key.
Starting stapling paper sheets after they have been distributed to all of the bins as taught in previously mentioned Japanese Patent Laid-Open Publications is not efficient because no stapling operations occur until paper sheets have been fully stacked on the last bin, i.e., despite that the other bins have already been loaded.
Further, assume that when a paper sheet associated with the last document is distributed to the first bin, a stapling operation begins at the first bin in order to enhance efficient stapling, as stated earlier. Such a scheme has a problem left unsolved, as follows. Specifically, since the stapling operation and the paper positioning operation are generally controlled independently of each other, the stapling operation at a certain bin and the paper positioning operation at the next bin may occur at the same time. However, if the timing for returning a stapled paper stack to the preceding bin at the end of the stapling operation and the timing for rotating a rotatable plate which forms part of paper positioning means to position a paper sheet discharged onto the following bin coincide with each other, the rotatable plate yields to the force of the stapled paper stack and thereby fails to accurately position the paper sheet on the following bin.
Another problem with the prior art copier is that when the desired number of copies is changed while a copying operation is under way in any of the two different staple modes, the paper sheets distributed to all of the bins are stapled. Hence, even incomplete sets of copy sheets are bound against the operator's intention.